mmterrill

well 1st my car wouldnt start so i bought a new battery. started fine but when i slow down at stops my rpm will fluctuate down to 500 then to 1000 almost stalling out. ive got no clue what it could be. belt, alt, timing belt? any ideas.

DennisS

Hey man....the same thing is happening to mine after I replaced the battery....did you find anything out about it/get it fixed? Any info would be greatly appreciated!
Thanks in advance!

$peed

I am assuming this is an automatic transmisison?

DennisS

Mine is.
I have done a little reading and it appears I am not alone. I think I may try cleaning the throttle body first. It makes sense that there is buildup of gunk that is causing the fluctuation. The battery dying may just be a contributing factor. The real cause of the rough idle is because the battery died I left it for a week untouched, thus letting the gunk build up and freeze? Anyway the process seems relatively easy and even a car idiot, such as myself, can do this without breaking anything (hopefully). I will update the post if this resolves anything but any more suggestions will be greatly appreciated!
Thanks again!

$peed

Ok,

Well not that I am saying this is the problem... but my buddy had some other car (not mazda) and a similar thing happened to him. People thought it was the Alternator, but it was only the RPMs that were fluctuating which meant it wasn't power related. What I told him it could be (ended up being true) was that his fuel pump was either jammed or not functioning properly and wasn't able to dleiver the fuel to the cylinders. If the pump is almost to the point where it will fail, you will see fluctuation. With my buddies car, it started out as fluctuation and then eventually just died. It restarted once more, fluctuated, then died... then it wouldn't start.

I think what happened was that the fuel pump would be supplying a variety of spurts of gas, which then causes different engine speeds. If the pump were to fail all together, then you would see your car shut off.

Something to look into... although I wouldn't know how to double check the fuel line to make sure the fuel pressure is adequate.

Let me know if anyone would know how to find that out? And if there is an easy fix or may need a new pump?

Hope this helps

p.s. - this wasn't for a mazda, so may be un-related... just thought to share wisdom of prior events

bam2k4

I too am having this problem. It's not my battery, thought it might be my alternator?
I'm headed to a mechanic on Friday and I don't want to get screwed, any words of wisdom would help.